A conventional driving apparatus of a laser scanner is designed as shown in FIGS. 2 to 4, which comprises a mirror 1, a differential speed increaser 2 as a displacement amplifying means, a lever 4 fixed on a shaft 3, a laminate type piezoelectric actuator 5 and a reaction spring 6.
The inputted driving signals give rise to a rectilinear displacement of the piezoelectric actuator 5, as shown by arrow A. Such a displacement is transmitted by way of a pin 7 to one end portion of the lever 4, which turns against a reaction force of the reaction spring 6, counterclockwise in the drawings. Together with the lever 4, the shaft 3 turns, transmitting the rotational displacement to the differential amplifier 2, where the turning is amplified and then transmitted to an output shaft 10. Then the mirror rotates predetermined degrees .theta., deflecting a laser beam coming from a laser beam generator (not shown). For the differential speed increaser 2, a Harmonic Drive (a trade name) is usually used.
The free end portion of the piezoelectric actuator 5 abuts the pin 7, which engages with a notch 11 formed in the end portion of the lever 4, as shown in FIG. 4. The free end portion of the reaction spring 6 contacts the other end portion of the lever 4 through a piston 12. (Reference can be made to Japanese Laid-open Nos. 61-132919 and 61-134726.)
In the above driving apparatus, in which the pin 7 is stopped by the notch 11 formed in one end of the lever 4, when the lever 4 is rotated .DELTA..theta. by the piezoelectric actuator 5, the supporting point of the lever 4 shifts with respect to the line of action of the piezoelectric actuator 5. Accordingly, there occur both shearing force F.tau. to the piezoelectric actuator 5 and a relative movement between the pin 7 and the end surface of the piezoelectric actuator 5. Therefore, a force acting transversely onto the piezoelectric actuator 5 is generated, which may break the actuator 5. Also, the relative movement between the actuator 5 and the pin 7 causes loss due to a friction, affecting the precision in the positioning.
The present invention solves these problems by providing a laser scanner driving apparatus which: eliminates the force transverse to the line of action of the actuator during the operation of the actuator; eliminates the loss due to friction on the end surface of the actuator during the operation; therefore eliminates fear of breaking the actuator; and improves the positioning precision of a laser scanner driving apparatus.